Antimicrobial penetrant-sealers.

The need for an antimicrobial penetrant-sealer became evident as the problem of flaking paint in food processing plants was explored. Flaking paint can fall into product, a situation which cannot be tolerated. The standards, set by the packing industry, for purity, freshness, and attractiveness preclude any foreign matter in product. Flaking paint as a problem has been with us since paint was first used. The many mechanisms involved in flaking of paint have been carefully studied. These mechanisms have been explained in detail, with accurate photographic records provided (Goll and Coffey, 1948; Goll and Hyde, 1952; Goll et al., 1952a, b; Eckhaus et al., 1953; York Research Corp. of Connecticut, 1952; Hunt, 1953; Buckman Laboratories, 1955; and Fisher, 1952). The problem was first confronted in the southern part of the country under hot, moist summer conditions. Two causes of this flaking paint soon became evident; one was ordinary wear as a result of processing methods, and the other was mold growth. Wear results from such extreme daily variations in temperature and humidity as occur in processing rooms, from the inevitable contact of minute particles of product (proteins and fats) with wall surface coverings, and, finally, from the use of cold water, strong detergents, hot water, and steam, as required by strict sanitary procedures in daily clean-up following processing. This wear accounts for a sizable proportion of the flaking paint. Mold growth causes the largest amount of flaking (Goll et al., 1952a, b), a fact which usually is not recognized. Mold removes the paint by growing on the wall underneath the paint, by growing on the paint side next to the wall and then forcing the paint off, by growing through the paint and thus getting between the paint and wall and then again forcing the surface covering off, and finally by growing on the paint and actually using the oils, minerals, and pigments in fungus metabolism, thus destroying the paint entirely (Hatfield, 1954). In order to combat the problem of flaking paint in the meat-packing industry, we undertook to develop and evaluate suitable antimycotic penetrant-sealers. An antifungal penetrant-sealer may be defined as a surface coating that prevents fungal growth, impregnates the material treated, and leaves no residual film which can be removed by ordinary wear. It became evident as the work proceeded that in penetrant-sealers we had a weapon which prevents many forms of microbial growth. Penetrant-sealers were formulated for application on both masonry and wooden surfaces. The characteristics required for penetration and surface covering varied with the materials tested. The masonry surfaces included cement, plaster, and brick used in building construction, whereas the wooden surfaces included not only those in building construction, such as walls, ceilings, cabinets and so on, but also those in the construction of transportation facilities, both refrigerated trucks and refrigerated railroad cars. Several kinds of woods are used. Each wood reacts to fungal attack differently (Vicklund and Manowitz, 1949a, b); however, in our experience with penetrants and sealers containing 0.1 per cent copper-8-quinolinolate, all woods were protected. The methods of applying penetrants and the concentration of antimycotic required for fungal protection for new wooden and masonry surfaces are entirely different from those required for these same surfaces after they have been in use. The daily contact of the surfaces with particles of meat and the effect of clean-up increased the difficulty of formulating adequate penetrant-sealers. Many of these surfaces have to be treated while wet to keep in order in step with production. Cooler walls, ceilings, and floors are examples in building surfaces. The wet floors of refrigerated trucks and railroad cars after clean-up are examples in transportation facilities. The paint companies cooperating in this work designed the formulas for meeting the problems encountered in the various materials treated and also made necessary changes in order to secure compatibility with the fungicide. One aim of the experiments reported in this paper was the development of laboratory and patch tests which would serve as a basis for selecting suitable penetrant-sealers for the field scale evaluation. Results from laboratory scale evaluation were compared with results from the patch panel tests, and the most promising candidates were subjected to field trial by treatment of refrigerated trucks and railroad cars and treatment of surfaces in processing establishments.